Summary
A certified flight instructor (CFI) and a commercial pilot were conducting a training flight to practice landings at nearby airports. After a normal pre-flight inspection and pre-takeoff engine check, the commercial pilot was flying. The flight to a local airport was described as uneventful by both pilots.
Flight and Incident
While turning onto the base leg of the traffic pattern, at a power setting of 1,900 rpm and an altitude of about 800 to 900 feet above ground level, the pilot attempted to increase engine power by moving the throttle forward. However, there was no response from the engine. The pilot informed the CFI, "there's no power." The CFI confirmed that the throttle was unresponsive and noticed that the engine rpm was slowly dropping.
Forced Landing
The CFI attempted to restart the engine without success and performed a forced landing to trees, which were located about 1/4 mile from the runway. Both pilots were wearing headsets and reported hearing no unusual noises or power changes prior to the loss of engine power.
Post-accident Examination
Examination of the wreckage did not reveal any pre-accident failures or malfunctions. The airplane had been operated for about 390 hours since new and was maintained under an approved manufacturer inspection program. Test-runs of the engine revealed a rich mixture operation in the idle and 400 pound airflow ranges, and an idle mixture rise of 120 rpm. Fuel flow checks of the fuel injector servo, flow divider, fuel nozzles, and lines revealed that the flow divider and nozzles met new production test specifications and exhibited no unusual characteristics. Examination of the fuel servo did not reveal any physical malfunctions; however, a flow check of the fuel servo revealed a mixture that exceeded the rich test specification limits during several test points. Despite the rich mixture indication observed during testing, at no time was a loss of engine power experienced.
Weather Information
The temperature and dewpoint reported at an airport about 18 miles south of the accident site were 82 and 61 degrees Fahrenheit, respectively.
Investigation Status
The investigation did not identify a specific cause for the loss of engine power, as no pre-existing mechanical issues were found and testing did not reproduce the power loss.